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| Argos Newsletter N° 48 - August 1994 |
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Paul W. Howey Microwave Telemetry Inc., |
Tracking the migration
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In order to track these birds PTTs weighing less than 30 grams were needed. Such a PTT on a 1000 gram bird would be only 3% of its body weight (the generally accepted limit is 5%). Ideally the PTTs would have a lifetime sufficient to track the fall migration south and the springtime return to the breeding grounds. In 1984 the first raptor was tracked by the Argos system, a Bald Eagle, Haliæetus leucocephalus, caught in the northern Chesapeake Bay which migrated south to Florida in the Fall of 1984. This was achieved by using a PTT that weighed about 200 grams. Ten years later the weight of the PTTs has been reduced to less than 30 grams. The Microwave Telemetry PTT 100 transmitter, which has been used over the last 3 years to track many different species of birds throughout the world, has been converted to a hybrid circuit (weighing a mere 3.5 grams). By using this together with the smallest high rate Lithium cells available and a light weight rugged housing, complete units ready to mount on birds weighing in the region of 28.5 grams are now available, with lifetimes of one year at an 8 hr on every 5 days duty cycle. At the time of writing (January 1994) six Peregrine falcons are being tracked by Argos. Two birds that were fitted with PTTs in Alaska have so far migrated south to Honduras, in Central America, and the Florida Everglades. Two birds tagged in Utah and Arizona are now in Central Mexico and Nicaragua. Another two birds tagged on the coast of Virginia, on their way south from the Arctic, are presently in Cuba and north west Argentina where they are overwintering. As the winter proceeds we hope to continue to monitor the progress of these birds and in the spring watch their return to their summer habitat. 
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Since we began experimenting with the Argos system in 1983 for the tracking of birds it
has been our goal to track the long distance migrations of the Peregrine Falcon, Falco
peregrinus, from its summer habitat in the North American Arctic and Greenland to its
wintering grounds, thought to be in Southern South America. Up until the present time the
routes taken by these birds on their fall and spring migrations have remained largely a
mystery, especially their movements south of latitude 20 deg. N. Their spring migrations
northwards do not seem to be simply a reverse of the Fall migration routes.